U.S. Pat. No. 4,879,296, issued Nov. 7, 1989 and U.S. Pat. No. 4,981,857, issued Jan. 1, 1991, disclose purine derivatives of Formula I described below, which are useful in the present invention. Methods of preparing the compounds are disclosed in both U.S. Pat. Nos. 4,879,296 and 4,981,857. The patents also disclose that the compounds provided therein are useful in human and veterinary therapy, particularly for conditions associated with the cell surface effects of adenosine. Even so, there is no disclosure in either U.S. patent that the compounds provided therein are useful as anti-obesity agents, or as agents capable of increasing the ratio to muscle mass to fat in farm animals. Instead, both patents are concerned with using the compounds disclosed therein in the treatment or prophylaxis of AIDS and other retroviral infections and for pathophysiological disorders arising from the cell surface effects of adenosine. Such pathophysiological disorders caused by adenosine/cell surface interaction are disclosed in both U.S. patents as including those arising within the cardiovascular, gastrointestinal or neuroendocrine systems, including heart block, asthma, and irritable bowel syndrome. U.S. Pat. No. 4,879,269 and 4,981,857 are each incorporated herein by reference, in their entirety.